High gel-strength hybrid hydrogels based on modified starch through surface cross-linking technique

Modification of starch with a microgel latex has been suggested as a novel method for preparing a hybrid hydrogel. The microgel latex, (poly (NaAA–AA–AM–AMPS)), was synthesized through inverse emulsion polymerization and used for modification of starch. The maximum absorbency of distilled water was achieved as 87 g/g for the hybrid hydrogel. A key advantage of this hybrid hydrogel is a high percentage (about 70%) of natural component. Since hybrid hydrogels are mechanically weak, the surface cross-linking technique was carried out to increase the gel strength and the absorbency under load (AUL), by employing 3-(2,3-epoxypropoxy) propyl trimethoxysilane. The AUL of hydrogels was increased from 6.5 to 17 g/g after surface cross-linking. The current hydrogels have overcome two limitations of hybrid hydrogels (i.e., low gel strength and low contribution of the natural part) which caused them not be commercial yet. Therefore, the current hydrogels have the potential to be used in agricultural applications, due to their high AUL and low acrylamide content.